This project concerns the role of palmitoyl coenzyme A hydrolase (EC 3.1.2.2) and acyl CoA hydrolases in the regulation of lipid metabolism. The hydrolase activities of rat submaxillary gland, brain, and other tissues will be measured under a variety of physiological, pharmacological, hormonal, and nutritional states of the rat to determine if this enzyme contributes to the modulation of intracellular concentrations of long-chain acyl CoA thioesters. Purification and characterization of the hydrolases from submaxillary gland and brain will be attempted. Mechanisms of regulation of these enzymes in vitro (i.e., product or substrate inhibition, allosterism, etc.) will be investigated and attempts made to correlate these findings with the physiology of the animal. In particular, the relationship between the secretory activity, energy production via lipid metabolism, and the activity of palmitoyl CoA hydrolase will be investigated.